This invention relates to a rectangular battery, and particularly to an improvement of the battery structure thereof.
The rectangular battery employed in such a device as a video camera has a structure in which cathode plates 101 and anode plates 102 are packed with separators 103 and alternately superposed, as shown in FIG. 1.
The layered product formed by these cathode plates 101, anode plates 102 and separators 103 is inserted into a rectangular battery casing having one side open, and then a liquid electrolyte is filled therein, to serve as a battery as a whole.
The cathode plate 101 is formed of a thin aluminum foil having both sides coated with a mixed cathode agent containing lithium. On the other hand, the anode plate 102 is formed of a thin copper film having both sides coated with a mixed anode agent containing carbon.
It is a conventional practice to sandwich the plural cathode plates 101 or anode plates 102 arrayed at predetermined intervals, with the pair of separators 103 in the direction of the thickness of the plates, as shown in FIG. 2, and then to bond portions between the electrode plates by heat melting so as to pack the plates. FIG. 2 shows only the case in which the cathode plates 101 are packed.
The heat melting is carried out by pressing with a temperature-controlled heater block. The packed electrode plates are separated at the fusing portions, as shown in FIG. 3, and the cathode plates 101 and the anode plates 102 are alternately superposed, as shown in FIG. 1.
However, since the separator 103 is excessively melted by heat propagation due to the heater block which presses the separator 103, the fusing portions need to be wider. For this reason, the electrode plates must be narrowed by the wider fusing portions, consequently reducing the battery capacity.
After the heat melting, the separator 103 may be crumpled by its contraction due to heat. This may conceivably cause deterioration in performance of the battery. Also, as a cutter is used to separate the electrode plates at the fusing portions, the fusing portion must be positioned correctly for each of the electrode plates. This raises a considerable problem in productivity.